qemuBuildMemoryBackendStr: Fix hugepages lookup process

https://bugzilla.redhat.com/show_bug.cgi?id=1196644

This function constructs the backend (host facing) part of the
memory device.  At the beginning, the configured hugepages are
searched to find the best match for given guest NUMA node.
Configured hugepages can have a @nodeset attribute to specify on
which guest NUMA nodes should be the hugepages backing used.
There is, however, one 'corner case'. Users may just tell 'use
hugepages to back all the nodes'. In other words:

  <memoryBacking>
    <hugepages/>
  </memoryBacking>

  <cpu>
    <numa>
      <cell id='0' cpus='0-1' memory='1024000' unit='KiB'/>
    </numa>
  </cpu>

Our code fails in this case. Well, since there's no @nodeset (nor
any <page/> child element to <hugepages/>) we fail to lookup the
default hugepage size to use.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

src/qemu/qemu_command.c

@@ -4778,23 +4778,28 @@ qemuBuildMemoryBackendStr(unsigned long long size,
             goto cleanup;
         }
 
-        /* Now lets see, if the huge page we want to use is even mounted
-         * and ready to use */
-        for (i = 0; i < cfg->nhugetlbfs; i++) {
-            if (cfg->hugetlbfs[i].size == hugepage->size)
-                break;
-        }
+        if (hugepage->size) {
+            /* Now lets see, if the huge page we want to use is even mounted
+             * and ready to use */
+            for (i = 0; i < cfg->nhugetlbfs; i++) {
+                if (cfg->hugetlbfs[i].size == hugepage->size)
+                    break;
+            }
 
-        if (i == cfg->nhugetlbfs) {
-            virReportError(VIR_ERR_INTERNAL_ERROR,
-                           _("Unable to find any usable hugetlbfs mount for %llu KiB"),
-                           pagesize);
-            goto cleanup;
-        }
+            if (i == cfg->nhugetlbfs) {
+                virReportError(VIR_ERR_INTERNAL_ERROR,
+                               _("Unable to find any usable hugetlbfs mount for %llu KiB"),
+                               hugepage->size);
+                goto cleanup;
+            }
 
-        VIR_FREE(mem_path);
-        if (!(mem_path = qemuGetHugepagePath(&cfg->hugetlbfs[i])))
-            goto cleanup;
+            if (!(mem_path = qemuGetHugepagePath(&cfg->hugetlbfs[i])))
+                goto cleanup;
+        } else {
+            if (!(mem_path = qemuGetDefaultHugepath(cfg->hugetlbfs,
+                                                    cfg->nhugetlbfs)))
+                goto cleanup;
+        }
 
         *backendType = "memory-backend-file";
 

tests/qemuxml2argvdata/qemuxml2argv-hugepages-numa.args

@@ -0,0 +1,46 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=spice \
+/usr/bin/qemu-system-x86_64 \
+-S \
+-M pc-i440fx-2.3 \
+-cpu Haswell \
+-m 1024 \
+-smp 2 \
+-object memory-backend-file,id=ram-node0,prealloc=yes,\
+mem-path=/dev/hugepages2M/libvirt/qemu,size=1073741824 \
+-numa node,nodeid=0,cpus=0-1,memdev=ram-node0 \
+-nodefaults \
+-monitor unix:/tmp/test-monitor,server,nowait \
+-rtc base=utc,driftfix=slew \
+-no-kvm-pit-reinjection \
+-global PIIX4_PM.disable_s3=1 \
+-global PIIX4_PM.disable_s4=1 \
+-boot c \
+-device ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x6.0x7 \
+-device ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,multifunction=on,addr=0x6 \
+-device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pci.0,addr=0x6.0x1 \
+-device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pci.0,addr=0x6.0x2 \
+-device virtio-serial-pci,id=virtio-serial0,bus=pci.0,addr=0x5 \
+-drive file=/var/lib/libvirt/images/fedora.qcow2,if=none,id=drive-virtio-disk0 \
+-device virtio-blk-pci,bus=pci.0,addr=0x7,drive=drive-virtio-disk0,id=virtio-disk0 \
+-drive if=none,media=cdrom,id=drive-ide0-0-0 \
+-device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
+-serial pty \
+-chardev socket,id=charchannel0,\
+path=/var/lib/libvirt/qemu/channel/target/fedora.org.qemu.guest_agent.0,server,nowait \
+-device virtserialport,bus=virtio-serial0.0,nr=1,\
+chardev=charchannel0,id=channel0,name=org.qemu.guest_agent.0 \
+-chardev spicevmc,id=charchannel1,name=vdagent \
+-device virtserialport,bus=virtio-serial0.0,nr=2,\
+chardev=charchannel1,id=channel1,name=com.redhat.spice.0 \
+-device usb-tablet,id=input0 \
+-spice port=0 \
+-vga qxl \
+-global qxl-vga.ram_size=67108864 \
+-global qxl-vga.vram_size=67108864 \
+-device intel-hda,id=sound0,bus=pci.0,addr=0x4 \
+-device hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 \
+-chardev spicevmc,id=charredir0,name=usbredir \
+-device usb-redir,chardev=charredir0,id=redir0 \
+-chardev spicevmc,id=charredir1,name=usbredir \
+-device usb-redir,chardev=charredir1,id=redir1 \
+-device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x8

tests/qemuxml2argvdata/qemuxml2argv-hugepages-numa.xml

@@ -0,0 +1,107 @@
+<domain type='qemu'>
+  <name>fedora</name>
+  <uuid>63840878-0deb-4095-97e6-fc444d9bc9fa</uuid>
+  <memory unit='KiB'>1572863</memory>
+  <currentMemory unit='KiB'>1048576</currentMemory>
+  <memoryBacking>
+    <hugepages/>
+  </memoryBacking>
+  <vcpu placement='static'>2</vcpu>
+  <os>
+    <type arch='x86_64' machine='pc-i440fx-2.3'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <features>
+    <acpi/>
+    <apic/>
+    <pae/>
+  </features>
+  <cpu mode='custom' match='exact'>
+    <model fallback='allow'>Haswell</model>
+    <numa>
+      <cell id='0' cpus='0-1' memory='1048576' unit='KiB'/>
+    </numa>
+  </cpu>
+  <clock offset='utc'>
+    <timer name='rtc' tickpolicy='catchup'/>
+    <timer name='pit' tickpolicy='delay'/>
+    <timer name='hpet' present='no'/>
+  </clock>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>restart</on_crash>
+  <pm>
+    <suspend-to-mem enabled='no'/>
+    <suspend-to-disk enabled='no'/>
+  </pm>
+  <devices>
+    <emulator>/usr/bin/qemu-system-x86_64</emulator>
+    <disk type='file' device='disk'>
+      <driver name='qemu' type='qcow2'/>
+      <source file='/var/lib/libvirt/images/fedora.qcow2'/>
+      <target dev='vda' bus='virtio'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
+    </disk>
+    <disk type='block' device='cdrom'>
+      <driver name='qemu' type='raw'/>
+      <target dev='hda' bus='ide'/>
+      <readonly/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0' model='ich9-ehci1'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x7'/>
+    </controller>
+    <controller type='usb' index='0' model='ich9-uhci1'>
+      <master startport='0'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0' multifunction='on'/>
+    </controller>
+    <controller type='usb' index='0' model='ich9-uhci2'>
+      <master startport='2'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x1'/>
+    </controller>
+    <controller type='usb' index='0' model='ich9-uhci3'>
+      <master startport='4'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x2'/>
+    </controller>
+    <controller type='pci' index='0' model='pci-root'/>
+    <controller type='ide' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/>
+    </controller>
+    <controller type='virtio-serial' index='0'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
+    </controller>
+    <serial type='pty'>
+      <target port='0'/>
+    </serial>
+    <console type='pty'>
+      <target type='serial' port='0'/>
+    </console>
+    <channel type='unix'>
+      <source mode='bind' path='/var/lib/libvirt/qemu/channel/target/fedora.org.qemu.guest_agent.0'/>
+      <target type='virtio' name='org.qemu.guest_agent.0'/>
+      <address type='virtio-serial' controller='0' bus='0' port='1'/>
+    </channel>
+    <channel type='spicevmc'>
+      <target type='virtio' name='com.redhat.spice.0'/>
+      <address type='virtio-serial' controller='0' bus='0' port='2'/>
+    </channel>
+    <input type='tablet' bus='usb'/>
+    <input type='mouse' bus='ps2'/>
+    <input type='keyboard' bus='ps2'/>
+    <graphics type='spice' autoport='yes'/>
+    <sound model='ich6'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
+    </sound>
+    <video>
+      <model type='qxl' ram='65536' vram='65536' vgamem='16384' heads='1'/>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
+    </video>
+    <redirdev bus='usb' type='spicevmc'>
+    </redirdev>
+    <redirdev bus='usb' type='spicevmc'>
+    </redirdev>
+    <memballoon model='virtio'>
+      <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/>
+    </memballoon>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -683,6 +683,14 @@ mymain(void)
     DO_TEST("pmu-feature-off", NONE);
 
     DO_TEST("hugepages", QEMU_CAPS_MEM_PATH);
+    DO_TEST("hugepages-numa", QEMU_CAPS_RTC, QEMU_CAPS_NO_KVM_PIT,
+            QEMU_CAPS_DISABLE_S3, QEMU_CAPS_DISABLE_S4,
+            QEMU_CAPS_DEVICE, QEMU_CAPS_VIRTIO_SCSI, QEMU_CAPS_DRIVE,
+            QEMU_CAPS_ICH9_USB_EHCI1, QEMU_CAPS_PCI_MULTIFUNCTION,
+            QEMU_CAPS_SPICE, QEMU_CAPS_CHARDEV_SPICEVMC,
+            QEMU_CAPS_VGA, QEMU_CAPS_VGA_QXL,
+            QEMU_CAPS_HDA_DUPLEX, QEMU_CAPS_USB_REDIR,
+            QEMU_CAPS_MEM_PATH, QEMU_CAPS_OBJECT_MEMORY_FILE);
     DO_TEST_LINUX("hugepages-pages", QEMU_CAPS_MEM_PATH,
                   QEMU_CAPS_OBJECT_MEMORY_RAM,
                   QEMU_CAPS_OBJECT_MEMORY_FILE);